The present disclosure relates to a semiconductor light emitting device and a method for manufacturing the same.
As shown in FIG. 9, a semiconductor light emitting device such as a light emitting diode (LED) has a light emitting part composed of a convex laminated structure 20 in which a first compound semiconductor layer 21 having an n-type conductivity type, an active layer 23 and a second compound semiconductor layer 22 having a p-type conductivity type are successively laminated on a substrate for manufacturing a semiconductor light emitting device (hereinafter sometimes referred to simply as “substrate 10”). A first electrode (n-side electrode) 140 is provided on the substrate 10 or an exposed portion 21a of the first compound semiconductor layer 21, and a second electrode (p-side electrode) 130 is provided on a top surface of the second compound semiconductor layer 22. Such a semiconductor light emitting device can be classified into two kinds of a semiconductor light emitting device of a mode in which light is outgone from the active layer 23 via the second compound semiconductor layer 22 and a semiconductor light emitting device of a mode in which light is outgone from the active layer 23 via the first compound conductor layer 21 (the latter will be referred to as “bottom emission type” for the sake of convenience).
In the related-art semiconductor light emitting device of a bottom emission type, for the purpose of maintaining luminous efficiency high, in general, as shown in FIG. 9, a reflective electrode for reflecting visible light from the active layer 23 is frequently used for the second electrode 130. The second electrode 130 as a reflective electrode is constituted of, for example, a lower layer 131 made of silver (Ag) and an upper layer (cover metal) 132 made of nickel (Ni) from the bottom (see, for example, C. H. Chou, et al., “High thermally stable Ni/Ag(Al) alloy contacts on p-GaN”, Applied Physics Letters, 90, 022102 (2007)). The upper layer 132 covers the lower layer 131. Here, by constituting the lower layer 131 of silver (Ag), a high light reflectance can be achieved. Also, by constituting the upper layer 132 of nickel (Ni), deterioration of the lower layer 131 to be caused due to oxidation is prevented, and occurrence of migration is prevented. In FIG. 9, a reference numeral 141 stands for an insulating layer; and each of reference numerals 142A and 142B stands for a contact part.
In general, the upper layer 132 is formed by a lift-off method. That is, after forming the lower layer 131, a resist layer 150 having an aperture 151 in a portion where the upper layer 132 is to be formed is formed on the basis of a photolithography technology (see FIG. 10A). Subsequently, the upper layer 132 is formed over the entire surface by a vacuum vapor deposition method (see FIG. 10B). Thereafter, by removing the resist layer 150 and the upper layer 132 located thereon, the second electrode structure shown in FIG. 9 can be obtained.